Explanation

The Stratosphere is the layer that generally begins around 10-50 km and extends up to about 50 km, which better fits the general range described than Exosphere. The Troposphere is the lowest layer, extending only up to about 10-15 km. The Mesosphere lies above the stratosphere but below the thermosphere, covering a different altitude range. The Exosphere is the outermost layer and does not start at 690 to 1,000 km from the surface.